Superconductivity of Dilute Primary Solid Solutions of In-Mg and In-Pb

By measuring magnetic moments and electrical resistances of pure indium and indium alloys containing 0.28 to 13.7 atomic per cent of magnesium and 0.06 to 0.73 atomic per cent of lead at liquid helium temperatures, the variation of the superconducting critical temperature, T_c, with the concentration of solute metals was studied. T_c decreases initially with the increasing concentration of solute in so far as a small amount of solute metals is concerned. When the amount becomes large, the alloying effect of magnesium differs from that of lead, i.e., in the former case T_c continues to decrease steadily, while in the latter it shows a gradual increase after passing through a minimum. These results qualitatively agree with the theoretical consideration of Anderson and of Nakamura. The threshold magnetic field at 0°K and the coefficient of electronic specific heat in the normal state were estimated from the data obtained